Much evidence suggests that coated vesicles (CV's) play a central role in a variety of selective membrane transport processes in cells including uptake and secretion of substances, recycling of secretory granule membrane, and insertion and removal of biologically important receptors. We have found that isolated brain CV's contain a Ca ions stimulated ATPase similar to that of the sarcoplasmic reticulum, as do CV's isolated from many other tissues. We hope to demonstrate that soluble clathrin, the coat protein of the CV, specifically recognizes the ATPase in membranes and removes it. We will investigate the role of calcium and ATP in CV fusion in vitro. We have found a specific CV-neurofilament interaction in vitro and will employ fluorescent anti-clathrin serum to search for such an interaction in cells, whih may provide a means for directed CV movements, using fluorescent microscopy. We will also use immune precipitation and sucrose gradients to obtain evidence for participation of CV's in transport of plasma membrane constituents from the site of synthesis in rough endoplasmic reticulum to the Golgi apparatus. The role of CV's in hormone receptor recycling will also be investigated using the above mentioned techniques.